Change of GTP-binding Protein in Hormone Producing Tumors of Rats

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We have been working on the function of ADP-ribosylation reaction in various cellular mechanisms including signal transduction and cell growth.ADP-ribosylation of GTP-binding proteins play important roles in cellular signal transduction, in particular, activation of adenylate cyclase system.Recent finding of mutation at the site of ADP-ribosylation of Gs and Gi proteins in hormone producing tumors of human by Bourne's group made us to investigate the similar changes in various tumors including experimental rat tumors of pancreas. Although we could not find the mutation in Gs proteins in various rat tumors but could find the mutation in one of the ten hormone producing human ovarian tumors. This is the first finding of the mutation of alpha subunit of Gs protein in human ovarian tumors. We could not find the mutation of Gi protein in our cases with hormone producing human ovarian tumors. We are currently identifying the exact site of mutation in the mutated Gsprotein in the ovarian tumor.